Demand valve



Oct. 7, 1958 R. D. cuMMlNs DEMAND VALVE Filed Oct. 17, 1955 @'Wc will Gap Mfm- United States Patent O DEMAND VALVE Richard D. Cummins, Tonawanda, N. Y., assigner to Firewel Development Company, Buffalo, N. Y., a cpartnership Application October 17, 1955, Serial No. 540,916

l 11 Claims. (Cl. 128-142) This invention relates to a demand valve such as used in conjunction with a face mask to supply pressurized oxygen or air in response to the reduced pressure in the mask caused by the inhalation of the wearer and which closes immediately following the inhalation so that the air or oxygen is supplied from the pressurized source only as required. The use of the invention is not, however, confined to air or oxygen masks, but may be used to control the supply of any gas in response to a demand for such gas as is evidenced by a reduced pressure on the outlet side of the valve.

An object of the invention is to supply such a demand valve which is sensitive so as to be opened with little effort on the part of the user and'is useful to supply air or oxygen from a high pressure source.

Another object is to provide such a demand valve which is partially self-energizing so that, once opened, it tends to keep itself open. By such characteristic, a mask equipped with the present demand valve causes less chest fatigue since while a certain amount of inhalation energy is required to open the demand valve, much less energy is required to hold the demand valve open in completing the inhalation so that little effort is required by the wearer of the mask for the greater part of each inhalation.

Another object of the invention is to4 provide such a demand valve operated by a diaphragm in a diaphragm chamber in which -the diaphragm chamber is isolated from pressure fluctuations, eddies or other turbulence in the stream of air or oxygen which it controls, thereby to render the chamber essentially responsive only to the demand of the user and to 'increase the sensitivity of the demand valve.

Another object of the invention is to provide a demand valve which can be located remote from the user and in which separate sensing and supply conduits are provided between the demand valve and the mask so that supplying oxygen or air to the mask does not adversely affect the sensitivity of the demand valve.

Another object is to provide `such a demand valve having a sensing conduit connecting it with the mask in which the sensing conduit can be of very small size, a conduit having a 1,68 inch inside diameter having been found entirely adequate to provide the required control.

Another object is to provide such a demand valve in which a very small diameter supply line can be provided to deliver air or oxygen from the demand valve to the mask, a supply line of la inch inside diameter having been found entirely adequate to provide the required air or oxygen.

Another object of the invention is to provide such a demand valve in which increased sensitivity by partial self-energization of the demand valve is created as a function of the flow of the air or oxygen from the demand valve to the mask.

Another `object is to provide such a demand valve which, in particular, supplies large volumes of air or oxygen at any pressure setting or at any altitude. With ice 2 conventional masks, the ow, that is liters per minute supplied, tends to drop o when larger volumes of air or oxygen are required whereas with the present demand valve, larger volumes of air or oxygen are supplied with substantially the same or even lessetfort than smaller volumes of air or oxygen.

Another object of the invention is to provide such a demand valve which is simple and reliable in construction and operation so as to be always operative without danger of leakage of the high pressure air or oxygen.

Another object is to provide such a demand valve which does not have critical tolerances or tits.

Other objects and advantages of the invention will be apparent from the following description and drawings in which:

Fig. 1 is a vertical section, partly in elevation, of a demand valve embodying the present invention and showing the same connected with a mask.

Fig. 2 is an enlarged section taken generally on line 2-2, Fig. l.

Fig. 3 is a perspective view, viewed from the bottom, of the upper stationary disk forming part of the demand valve.

Fig. 4 is a perspective view, viewed from the top, of the lower stationary valve disk forming part of the demand valve.

The demand valve of the present invention is shown as used in conjunction with supplying air or oxygen from a relatively high pressure supply line represented by the nipple 5 to a mask 6 having a nipple 8 through which the air or oxygen is admitted. The mask 6 is applied to the face of the user, such as an aviator intending to fly at high altitudes, so that a reduced pressure in the internal chamber 9 of the mask results on each inhalation of the wearer of the mask. By relatively high pressure oxygen or air supply is meant pressure in the order of from, say, 5 to 100 pounds gage pressure.

The high pressure air or oxygen inlet nipple 5 is screwed into the rim 10 of a metal shell 11, this rim surrounding a large opening in the side of the shell. A diaphragm 12 extends across this opening and is secured to the rim 10 by a cap 13. The cap 13 can be secured to the rim 10 by screws 14 or in any other suitable' manner, the margin of the diaphragm 12 being clamped by the cap 13 against the rim 10 so as to provide an ambient air chamber 15 between the diaphragm 12 and the cap 13. This chamber is at ambient air pressure because of a vent 16 provided in the cap 13.

A demand chamber 20 is formed on the side of the diaphragm 12 opposite the ambient air chamber 15, this demand chamber 20 being in part formed by an internal partition 2l extending transversely across the shell 18. Adjacent the high pressure inlet nipple 5 and between the diaphragm 12 and the partition 21, the rim 10 of the shell 11 is formed to provide a cylindrical recess or bore 22 which opens into the demand chamber 20 and has its axis directed toward the center of the diaphragm 12 which preferably has secured thereto a metal plate 23 on the side forming the demand chamber 20. The bottom of the cylindrical bore or recess 22 forms an annular seat or shoulder 24 facing the diaphragm 12 and surrounding a passage 25 communicating with the high pressure y nipple 5.

A metal washer 26 seats against the shoulder 24 and onithis washer 26 is seated a rubber disk 28 provided with a coaxial opening which registers with a smaller opening provided in a lower stationary valve disk 29. This lower stationary" valve disk 29 has a raised rim 30 which supports an upper stationary valve disk 31 in such manner as to provide a chamber 32 between the stationary valve disks 29 and 31. This chamber 32 has an opening 33 registering with a passage 34, the latter discharging into a chamber 35 between the partition 21 and a second partition 36 which extends transversely across the shell 11 on the side of the partition 21 opposite the demand chamber 20.

`The upper stationary valve disk 31 is provided with a'downwardly directed teat 38 having a through opening through which the stem 40 fixed to a valve head 41 extends, this valve head 41 being cup-shaped with its rim bearing against the underside of the rubber disk 28 around the central opening therethrough. To insure against pressures building up within the teat 38, this teat is preferably provided with a side opening 41 which is directed toward the outlet passage 34 as best shown in Fig. 1. A ring 42 having a large central opening 43 holds the stationary valve disks 29 and 31 in the bore 22.

An important feature of the invention resides in the clamping of the rim of a cup-shaped rubber seal 44 between the ring 42 and the upper stationary valve disk 31. Ihis rubber seal 44 is made in the form of a rubber membrane and has a cup-shaped part which projects into the demand chamber 20, this cup-shaped part having a conical center which extends toward the valve head 41 and is provided with a central sleeve 48 which tightly embraces the valve stem 40. It will be seen that this cup-shaped seal 44 positively prevents the escape of high pressure air past the demand valve directly into the demand chamber 20 to cause turbulence or uctuation of pressures therein.

The upper end of the stem 40 can terminate in a knob 49 which is arranged to engage the plate 23 on the diaphragm 20.

Another chamber 50 is formed between the rear wall of the shell 11 and the partition 36 and this rear wall is provided with a boss 51 having an internally threaded bore 52 into which a screw fitting 53 is secured to be in communication with the chamber 50. A flexible supply tube 54 can connect the fitting 53 with a tube 55 tted in a sleeve 56 in the rubber nipple 8 of the mask 6. This exible supply tube 54 is the line which supplies the air or oxygen to the mask 6 and it is entirely practicable that this supply line be of a very small cross sectional size. It has been found that a supply line 54 of A inch inside diameter size is entirely practicable.

'I'he fitting 53 is in axial alinement with an opening 60 in the partition 36. This opening 60 is in turn in line with a short tube 61, one end of which is fitted in an opening 62 in the partition 21 to project from this partition. 'I'he outboard end of the tube 61 terminates closely'adjacent the rim of the opening 60 so as to have an injector etect. Thus, the passage of the air from the chamber 35 through the marginal part of the opening 60 serves to induce a reduced pressure within the tube 61. This in turn serves to provide a reduced pressure within the demand chamber 20.

The movement of the diaphragm 12 is under control of a sensing conduit 65 which is independent of the supply line 54. This sensing conduit comprises a screw fitting 66 screwed into the rim 10 of the casing 1l and communicating with the demand chamber 20 by means of a passage 68. A metal tube 69 extends from the tting 66 toward the outlet end of the screw fitting 53 and connects with a rubber tube 70. This rubber tube can extend alongside the supply tube 54 and can be of very much smaller diameter, it being entirely practicable to have the sensing tube 70 of a M6 inch inside diameter.

The opposite end of the rubber sensing tube 70 connects with a metal tube 71 which extends through the In the operation of the demand valve, when the wearer of the mask 6 inhales, the pressure in the mask chamber 9 is, of course, reduced. This, through the sensing conduit 65, causes a reduction in pressure in the demand chamber 20. Reduction in pressure in the demand chamber 20 is also caused through the supply line 54, chamber 50 and tube 61 since at this time, no air or oxygen is flowing through this supply line 54. It is a feature of the invention, however, that after the flow of air or oxygen under pressure through the supply line 54 starts, the reduction in pressure in the demand chamber 20 is essentially under control of the sensing conduit 65 and that this reduction in pressure in the demand chamber 20 is `in large part maintained through induction by the flow of the oxygen or air supplied through the supply line 54.

The reduction in pressure in the demand chamber 2l causes the flexible diaphragm 12 to move to the left and hence to move the outer end of the valve stem 39 to the dotted line position shown in Fig. 1. This tips the cup shaped valve head 41 to the dotted line position shown in this ligure and hence air or oxygen under the assumed relatively high pressure from the supply nipple 5 is now free to flow from the passage 25 past the open valve head 41 into the chamber 32 between the stationary valve disks 29 and 31 and thence through the passage 34 into the chamber 35 and from this chamber through the opening 60, chamber 50, flexible supply line 54, tube 55 and nipple 8 into the interior chamber 9 of the gas mask I to meet the inhalation requirements of the wearer of the mask.

Such high pressure air as may enter through the end opening of the nipple 38 up the upper stationary valve disk 31 is prevented from escaping into the demand chamber 20 because of the cup-shaped exible valve seal 44 which has its inner part snugly fitted around the valve stem 39 and its outer part snugly clamped against the upper face of the upper stationary valve disk 31 and at the same time leaves the valve stem 39 free to move in response to the movement of the diaphragm 12. Such oxygen or air under pressure as does so enter the end u opening of the nipple 38 is free to escape through the side of the tube 55 and terminates in an outboard end 72 which is arranged coaxially of the tube 55 and directed toward the interior ofthe mask. This tube 55 produces an injector effect against the end 72 of the sensing conduit, the air supplied to the mask from the supply line 54 inducing a reduced pressure at the end of the metal tube 72 so as to create a reduced pressure in the sensing conduit and hence in the demand chamber 20.

side vent 4l in this nipple and join with the main stream of air llowing to the mask.

In owing through the opening 60 in the transverse partition 36, the main stream of air or oxygen ows along the edge of the outboard end of the tube 61 thereby to provide anI aspirating etect upon this outboard end of this tube 61 so as to induce a suction at this outboard end of this tube. This reduces the pressure in the demand chamber 20 so as to tend to hold the diaphragm 12 to the right and the valve head 41 open. Accordingly, the relation of the outward end of the tube 61 to the opening 60 tends to make the demand valve partially selfenergizing when once open so that little elort is required by the user of the mask in continuing his inhalation, thereby to reduce chest fatigue.

The demand valve is further rendered self-energizing by the aspirating effect of the air or oxygen supplied to the mask along the outboard end 72 of the tube 71 at the mask end of the sensing line 65. Thus, the air entering the mask 6 ows along this outboard end 72 of the tube 71 so as to induce suction in this tube 71 which,A through the sensing line 65, tends to maintain the reduced pressure in the demand chamber 20 necessary to hold the valve head 41 open. It will accordingly be seen that when once open, the demand chamber tends to hold itself open by the aspirating effect produced at the outboard ends of both of the tubes 61 and 71.

When the user completes his inhalation, the ow of air oxygen through the supply line 54 is immediately reduced to a point where the aspirating effect upon the outboard ends of the tubes 61 and 71 is insufficient to maintain that reduced pressure in the demand chamber 20 necessary to hold the valve head 47 open. Accordingly, this valve head assumes the closed full line position shown in Fig. 1 and remains closed until thewearer of the mask 6 again inhales and repeats the cycle as above described.

With the demand valve -of the present invention, it has been found that the flow of air or oxygen does not fall off as increased amounts are required as with conventional demand valves. Thus, with a conventional valve, as increased ow of air is required, a very substantially greater effort is required to produce such ow.` With the present demand valve being partially self-energizing,

less etort is required to produce maximum ow of air or oxygen than is actually required to produce smaller amounts of air or oxygen.

It will particularly be noted that the demand chamber 20 is isolated from the How of air or oxygen to the mask 6 so that the pressure in this demand chamber 20 is not subject to uctuations due to any eddies, pulsations or irregularities in the ow of the stream of air or oxygen to the mask. Instead, once the inhalation has started the ow of air or oxygen to the mask, the degree to which the valve head 41 is opened or closed and closing of this valve head is essentially under control of the sensing line 65 which responds, of course, to the demand of the user.

From the foregoing, it will be seen that the present invention provides a very simple and reliable demand valve in which chest fatigue is greatly reduced by rendering the demand valve self-energizing after being once opened at the start of an inhalation. It will further be seen that the operation of the demand valve is essentially responsive only to the inhalation demand of the user and not to I eddies, fluctuations or turbulence in the air or oxygen supplied. It will also be seen that the demand valve of the present invention permits of the use of very small diameter supply lines 54 and sensing line 68 thereby to provide the minimum impedance to the free movement of the head of the wearer of the mask.

I claim:

1. A demand valve of the character described, comprising a shell provided with an opening in its side, a flexible diaphragm extending across said opening and forming with said shell a demand chamber, the opposite side of said diaphragm being subject to ambient pressures, a gas inlet and a gas outlet connecting with said shell and connected with each other by a passage through said shell, valve means across said passage and including a stem extending into said demand chamber to be actuated by movement of said diaphragm in contracting said demand chamber to open said valve, a supply conduit connecting said gas outlet with the internal chamber formed by a mask, and a Isensing conduit providing communication between said internal chamber of said mask and said demand chamber, the outlet end of said sensing conduit being arranged in and opening in the direction of the flow of gas through said supply conduit thereby to produce a suction in said sensing conduit in response to the ow of gas through said supply conduit.

2. A demand valve as set forth in claim l wherein said sensing conduit is of substantially smaller linternal diameter than said supply conduit.

3. A valve as set forth in claim l wherein said outlet end of said sensing conduit is arranged generally concentric with said supply conduit.

4. A demand valve as set forth in claim l wherein said open end is in said internal chamber of said mask adjacent to discharge end of said supply conduit.

5. A demand valve of the character described, comprising a yshell provided with an opening in its side, a flexible diaphragm extending across said opening and forming with said shell a demand chamber, the opposite side of said diaphragm being subject to ambient pressures, a gas inlet and a gas outlet connected with said shell and connected with each other by a passage through said shell, a pair of stationary valve disks seated in a bore leading to said demand chamber and forming between them a chamber communicating with said gas outlet, said valve disks each having a hole therethrough, the outer face of the valve disk remote from said demand chamber forming a wall of that end of said passage communicating with said gas inlet, a cup-shaped valve head having its rim seated against said outer face and around the central hole of the valve disk remote from said demand chamber, a stem fast to said valve head and extending through said central holes into said demand chamber and into operative relation with said diaphragm,'exible sealing means between said valve stem and the valve disk adjacent said demand chamber, a supply conduit connecting said gas outlet with the internal chamber formed by a mask, and a sensing conduit providing communication between said internal chamber of said mask and said demand chamber.

6. A demand valve as set forth in claim 5 wherein said flexible sealing means comprises a cup-Shaped exible chamber having a central opening in which said valve stem is fitted, and a clamping ring holding the rim of said flexible member against said valve disk adjacent said demand chamber.

7. A demand valve of the character described, comprising a shell provided with an opening in its side, a partition extending across the interior of said shell and forming a first chamber therein, a exible diaphragm extending across said opening and forming with said shell and partition a demand chamber on the opposite side of said partition from said first chamber, the side of said diaphragm opposite said demand chamber being subject to ambient pressures, said partition being provided with an opening into said demand chamber, a gas inlet and a gas outlet connecting with said shell, means in said shell providing a passage, including said first chamber, connecting said inlet and outlet and producing a suction at said opening into said demand chamber in response to the flow of gas through said passage, valve means across said passage and including a stem extending into 'said demand chamber to bev actuated to open said valve in response to movement of said diaphragm in contracting said demand chamber, and a supply conduit adapted to connect said gas outlet with the internal chamber formed by a mask.

8. A demand valve of the character described, comprising a shell provided with an opening in its side, a flexible diaphragm extending across said opening and forming with said shell a demand chamber, the side of said diaphragm opposite said demand chamber being subject to ambient pressures, said shell being provided with an opening into said demand chamber, a tube tted in said opening and having an outboard end projecting away fromsaid demand chamber, a gas inlet and a gas outlet connecting with said shell, means in said shell providing a passage connecting said inlet and outlet and including means arranged to concentrate the stream of gas owing through said passage to ow along the outboard end of said tube in the direction to induce a suction in said tube and thereby produce a suction in said demand chamber in response to the flow of gas through said passage, valve means across said passage and including a stem extending into said demand chamber to be actuated to open said valve in response to movement of said diaphragm in contracting said demand chamber, and a supply conduit adapted to connect said gas outlet with the internal chamber formed by a mask.

9. A demand valve of the character described, comprising a shell provided with an opening in its side, a partition extending across the interior of said shell and forming a first chamber therein, a flexible diaphragm extending across said opening and forming with said shell and partitic-n a demand chamber on the opposite side of said partition from said rst chamber, the side of said diaphragm opposite said demand chamber being subject to ambient pressures, said partition being provided with an opening into said demand chamber, a tube fitted in said opening and having an outboard end projecting away from said demand chamber, a gas inlet and a gas outlet connecting with said shell, means in said shell providing a passage, including said lirst chamber, connecting said inlet and outlet through said first chamber, means arranged to concentrate the stream of gas owing through said passage to ow along the outboard end of the tube in the direction to induce suction in said tube and thereby produce a suction in said demand chamber in response to the ow of gas through said ipassage, valve means across said passage and including a stem extending into said demand chamber to be actuated to open said valve in response to movement of said diaphragm in contracting said demand chamber, and a supply conduit adapted to connect said gas outlet with the internal chamber formed by a mask.

10. A demand valve of the character described, comprising a shell provided with an opening in its side, a exible diaphragm extending across said opening and forming with said lshell a demand chamber, the side of said diaphragm opposite said demand chamber being subject to ambient pressures, said shell being provided with an opening into said demand chamber, a gas inlet and a gas outlet connecting with said shell, means in said shell providing a passage connecting said inlet and outlet and producing a suction at said opening into said demand chamber in response to flow of gas through said passage, a supply conduit adapted to connect said gas outlet with the internal chamber formed by a mask, and valve means across said passage and comprising a pair of stationary valve disks seated in a bore leading to said demand chamber and forming between them a chamber communicating with said gas outlet, said valve disks each having a central hole therethrough, the outer face of the valve disk remote from said demand chamber forming a wall at that end of said passage communicating with said gas inlet, a cupshaped valve head having its rim seated against said outer face around the central hole of the valve disk remote from said demand chamber, a stem fast -to said valve head and extending through said central holes into said demand chamber and into operative relation with said diaphragm, and liexible sealing means between said valve stem and said valve disks.

ll. A demand valve as set forth in claim 10 wherein said sealing means comprises a cup-shaped flexible member having a central opening in which said valve stem is fitted, and a clamping ring holding the rim of said exible member against the valve disk adjacent said demand chamber.

References Ci'ted in the file of this patent UNITED STATES PATENTS 2,630,129 Holmes Mar. 3, 1953 FOREIGN PATENTS 663,202 Great Britain Dec. 19, 1951 

